Hablu likes odd numbers a lot. So he wants the sum of all odd numbers in range [a, b]. That is, find the sum of all odd numbers i such that (a ≤ i ≤ b). Seems easy right? Because it is.

Input

The first and only line will contain 2 integers a, b where (0 ≤ a ≤ 10⁸) and (0 ≤ b ≤ 10⁸).

Output

In one line, output the value of the sum

Example

Input:
0 9

Output:
25